PURPOSE: To improve the operability at the time of data transmission and reception.

CONSTITUTION: When a communication is not currently in process (S2), data transmission is not performed and a file is stored in an external storage device (S3). When the communication is in process (S2), on the other hand, LSD communication capability is checked (S4). When no LSD communication capability is available (S4) and an opposite terminal has no LSD capability (S5), contents of 'A data communication can not be made since the opposite terminal has no LSD capability' are displayed on an image monitor (S7). When the opposite terminal has the LSD capability (S5), the LSD capability of this terminal is set to presence (S6). An LSD transmission mode is set (S8), a data file to be sent is compressed (S9) and sent (S10), and after the data transfer, the LSD transmission mode is turned OFF to release the transfer rate assigned to the data transfer (S11).